"What is email marketing?" Fair question. Unlike one-to-one messages, email marketing entails sending one message to many people—sometimes thousands. It's permission-based, which means your readers must opt in to your newsletter, and you need to explain to them why they're receiving it. Because personal email services like Gmail or Yahoo limit the amount of people you can send to at one time, an email service provider like MailChimp is the best way to send email marketing. ESPs will manage your delivery infrastructure, help keep your messages away from spam filters, and generally do a lot of not-fun-but-necesssary work for you.

People send all sorts of fantastic email newsletters to their fans, and we hope this guide will help you do the same. Now, let's get started.

How HTML Email Works

Before you can start designing, coding, writing, and sending HTML emails, you need to know how they work and what tools you'll need.

Multipart/Alternative MIME format

The most important thing to know about HTML email is that you can’t just attach an HTML file and a bunch of images to a message, then click send. Most of the time, your recipient's email application will break all the paths to your image files by moving your images into temporary folders on the recipient's hard drive. You can’t just paste all your code into your email application, either. Most email apps send messages in plain-text format by default, so the HTML won’t render. Your recipients would just see all that raw source code, instead of the pretty email that you made them.

Instead, you need to send HTML email from your server in multipart-alternative MIME format. That means your mail transfer agent bundles your HTML code, plus a plain-text version of the message, together into one email. That way, if a recipient can’t view your beautiful HTML email, the good old, reliable plain-text version of your message is displayed. It’s kind of a nerdy thing, which is why a lot of people mess it up when they try to send HTML email themselves. You either need to program a script to send email in multipart-alternative MIME format, or use an outside vendor (like MailChimp) to deliver email for you.

Delivering HTML email

Lots of email marketing newbies make the mistake of setting up forwarding lists, or CC’ing copies of a message to all their customers. This causes all kinds of problems—especially when a customer clicks “reply-all.” First of all, there’s no way to track or personalize for a big group like that. And most importantly, it just looks unprofessional and impersonal when recipients can see your entire list of other recipients. (All this without mentioning the privacy concerns of exposing a bunch of email addresses like that.)

That’s why when an email-marketing system like MailChimp sends your campaign, we take your message and send it one at a time to each recipient on your list (really, really fast). Unlike your work computer linked to your local ISP, which probably has a standard monthly bandwidth limit, email-marketing vendors use dedicated mail servers capable of sending hundreds of thousands of emails per hour.

Email delivery considerations

Sending a mass email comes with a handful of delivery considerations. For instance, if you send from your own server, your ISP may throttle your outgoing emails or shut down your account if you send too much too fast. They may also shut you down if you exceed your monthly bandwidth limit.

Email firewalls and ISPs that receive your campaigns don’t like receiving tons of emails from a single IP address at once (unless they normally receive tons of emails from that IP). So if you only send occasional email campaigns from your IP, you may want to throttle your delivery or spread them across multiple IPs, to avoid accidental blocking. Email-marketing services usually split your campaign into pieces and send it out over lots of different IP addresses to avoid this issue. If you send emails from your desktop email program, chances are you’re connecting through your local ISP. If you don’t have a dedicated IP address set up with your ISP, you’re probably sending emails from a dynamic IP address. ISPs and spam filters don’t like receiving lots of emails from a dynamic IP address, because it looks like a hijacked home computer. If you’re not using an email-marketing vendor like MailChimp, you should always send from a dedicated IP address.

For more information on how HTML email works, visit MailChimp's Email Template Reference.

Common Mistakes

There are a lot of common mistakes people make when creating HTML emails. From sending without permission to confusing transactional emails with email marketing, from purchasing email lists to writing like a used-car salesman, there are several things you should keep in mind while creating your campaigns. MailChimp's Common Rookie Mistakes guide is a great place to start. Give it a scan before starting your first email marketing campaign.

Designing and Coding

Now that you have a solid understanding of how HTML emails work, we can get to the fun stuff: designing and coding your emails. Use existing materials to craft the tone and look of your email into a solid and effective layout. Keep your design simple and straight forward, focus on your message, not your craftiness.

Focus on typography first. The type is the one thing that is consistently rendered across different email clients. Most email clients block images from first-time senders by default, so your subscribers will almost always see the text of your email before they see anything else. Your message should still come across without images.

Keep in mind that your email's layout should stay right around 600 pixels in width. Many email clients provide a preview window that's rather narrow, and this helps to ensure your entire design will be visible. Even with the limit of 600 pixels, there are plenty of ways for you to lay out your content to create a clean-looking design for viewing in standard email clients or on mobile devices.

To delve into the specifics of designing your email, visit MailChimp's Email Template Reference.

Avoiding Spam Filters

Spam is unsolicited email sent to a list of people. The CAN-SPAM Act, which became law on Jan. 1, 2004, dictates that you can be fined $11,000 for every offense. (Multiply that by every person on your list, and you'll see how spam can get expensive in a hurry.) If you send email marketing, you should read the CAN-SPAM Act and understand the rules.

But even innocent email marketers sending to permission-based lists sometimes get into spam-filter trouble. The only way to avoid this is to understand how spam filters work. MailChimp's How to Avoid Spam Filters guide explains the criteria involved in determining spam, and offers plenty of practical tips to help keep your emails out of the junk folder.

Testing Your Email Designs

Once you've designed and coded your first HTML email template, it's time to test. Don't just write your content and start sending. Instead, make sure your template will work in the many email applications out there. Once you've found and fixed the inevitable bugs, then it's time to send.

Check different services and ISPs

Some applications take spam filters very seriously. Others will strip your BODY or HEAD tags, or content below a certain line. Flash doesn't work with some, many will block images by default. The bottom line is it's important to see how your email will look in as many different scenarios as possible.

Send tests to friends and co-workers

For many, it's difficult to set up test computers or test in many different applications. But by keeping your designs simple and sending to a few friends or colleagues, you can be sure to catch broken images, typos, and other bugs.

Inbox Inspector and Delivery Doctor

If you use MailChimp, we provide a couple testing features for monthly users. Inbox Inspector will automatically select the 10 most-used email clients from your subscriber list, then show you screenshots of your email in each. It also gives you a spam analysis based on words and phrases that trigger filters. Delivery Doctor sends a bunch of tests, changing multiple aspects of your campaign, to see how it fares against spam filters and consumer ISPs. If it finds a problem, it'll give you the diagnosis and a suggested fix.

Measuring Performance

You've designed, coded, wrote, tested, and sent your first email marketing campaign. Maybe you've sent several, in fact, and you're starting to wonder if your email-marketing efforts are worth the effort. How can you measure your performance, figure out what's working and what could use some work? There's data you should observe and questions you should ask to make these decisions.

Click rate

How many people clicked links in your email? Which links did they click the most? Did they click on product links, or research links? Did you see a rise in purchases? How long after you sent the campaign do links keep getting clicked?

Unsubscribe rate

What’s your unsubscribe rate after each campaign? Less than one percent is average for lists that are contacted regularly, and well maintained. If you send very infrequently or if it’s your very first send, your unsubscribe rate may be much higher. Check your rate after each campaign. If you see it spike after a particular campaign, see if it had anything to do with your content. Maybe you’re sending too frequently. Maybe not frequently enough.


Watch your bounce rate after each campaign. A good list-management system will break down your bounces into “hard” vs. “soft,” and clean your list for you. Soft bounces are emails that exist, but for some reason, they couldn’t be delivered. For instance, their server might have been too busy at the time of your delivery. Hard bounces are undeliverable—perhaps the email account doesn’t exist anymore, or there was a typo in the address. Hard bounces should be removed immediately.

For more information about tracking your email and how MailChimp can help, check out our Understanding Reports guide.

Website traffic

Check your website traffic logs after each email campaign. Does traffic pick up? Do orders increase? Was the spike in traffic immediate, or was it more like a gradual wave? How long does the new traffic last (and how long should you keep the graphics and pages that your email points to hosted live)?

Signups since last campaign

After each campaign, do you get lots of new subscribers? That could mean your loyal readers are forwarding your emails to friends. How nice! Your content is actually useful! Don’t see any list growth at all? Maybe you need to make your content more interesting or relevant to your customers.

MailChimp integrates with Google Analytics to further illustrate how your emails affect website traffic and drive revenue. Our How to Use Google Analytics With MailChimp guide is a great place to start.

Goooal allows you to add subscribers to MailChimp static segments based on the pages on your site they visit from your email campaigns. Sort your readers by interests so that they only get emails they care about.


At this point, you should have a pretty good handle on the world of email marketing and how it can help your business. But everyone can get better. Try these MailChimp resources if you're looking to really dig in.

MailChimp's guides and studies are thorough, thoughtful looks at various angles of the email marketing industry.


Our Email Template Reference goes over all the HTML email basics, including further resources.


Featuring hundreds of elegant, smartly done email newsletters, MailChimp's inspiration board is a great answer to the question, "What should I include in my emails?"


Looking for some one-on-one help with your email marketing? Check out MailChimp's Experts directory.